Method for casting concrete foundation



May 6, 1969 A. A. SOLLAY 3,442,089

` METHOD FOR CASTING CONCRETE FOUNDATION Filed Jan. 25, 1967 NM V NM.ggf

ATTORNEYS 3,442,089 METHOD FOR CASTING CONCRETE FOUNDATION i Alva A.Sollay, P.O. Box 5731, Drew Station, Lake Charles, La. 70601 Filed Jan.25, 1967, Ser. No. 611,681 Int. Cl. E02d 5/34; E04b 1/16 U.S. Cl.61-53.64 9 Claims ABSTRACT OF THE DISCLOSURE The present inventionrelates to a concrete foundation for buildings, bridges and otherstructures, which comprises a cast in situ, at least mostlysubterranean, annular concrete pillar having a removable central core ofsand or similarly substantially non-cohesive material supported upon anaxially short cast-in-situ concrete plug. The invention also relates toa method for forming the foundation which comprises digging, drilling orotherwise forming a shaft in the earth, placing a smaller O.D. tubularcasing in the shaft, filling the shaft/casing annulus with concrete,pouring an axially short plug of concrete into the casing throughbore;depositing sand or a similarly noncohesive, non-cementitous coring,filler material into the casing throughbore above the plug tosubstantially lill the throughbore; longitudinally removing the casing;allowing the concrete to harden and preferably removing the coring. Thisabstract, because of its brief and introductory nature, should not beconstrued as being all inclusive or as in any way limiting the scope ofthe claims appended to this specication or the range of applicability ofthe principles described herein. This abstract is chiefly intended as anaid to persons scanning this document for the rst time in quicklyascertaining whether the disclosure on this document may warrant theirfurther study.

BACKGROUND OF THE INVENTION Concrete foundations of the general typeover which the present invention is an improvement are those used tosupport buildings, bridges, and such structures. Customarily, such priorart foundations have been formed in place by boring, drilling orotherwise forming a vertical shaft in the earth and filling the shaftwith concrete. After the concrete has hardened, the intended structurecan be supported thereon. The inventor herein has found that theconcrete along the longitudinal centerline of such prior artfoundations, at least over most of the depth of such foundations can beeliminated without a corresponding sacrifice in strength when theconsiderations related hereinafter are described.

OB] ECTS OF THE INVENTION It is an object of the invention to provide animproved foundation for buildings, bridges and the like which is easy toemplace and which is conservative of expensive materials.

Another object of the invention is the provision of a method for castingannular, mostly subterranean, concrete foundations in situ whichprovides necessary forms for the concrete but allows for their removalwhile the concrete is still unhardened.

A further object of the invention is the provision of an annular mostlysubterranean cast-in-place concrete foundation having a concrete plugblocking the lower end of the bore of the annular concrete member and acore of sand or like -material supported upon the plug at least untilthe concrete of the annular member has hardened.

DEFINITIONS As used herein the term concrete is intended to encompassthe material brought into being when portland 3,442,089 Patented May 6,1969 ICC cement, water and sand plus gravel, crushed stone or otheraggregates are mixed together; the term is also intended to encompasssuch materials wherein portland cement is replaced in whole or in partby other cements known in the construction industry to be useful forsuch replacement. An exemplary enumeration of cements can be found underthe heading Cement, Types of Cement, on pages 690-697 of Kirk-Othmer,Encyclopedia of Chemical Technology, vol. 4, 2nd Ed.,I IntersciencePublishers, Division of John Wiley and Sons, Inc., New York 1964).

SUMMARY OF THE INVENTION The present invention has both method andarticle aspects.

The method of the present invention includes:

(a) Making a shaft in the earth;

(b) Inserting a tubular casing in the shaft so as to extend throughoutsubstantially the full depth of the shaft said casing having an externaldiameter that is smaller than the diameter of said shaft, therebydefining a shaft/ casing annulus exteriorly of the casing;

(c) Filling plastic unhardened concrete into the annulus;

(d) Depositing an axially short plug of plastic unhardened concrete inthe casing interiorly thereof at the lower end thereof;

(e) Filling the casing interiorly thereof above said plug with asubstantially non-cohesive, granular material substantially to theheight of concrete in said annulus.

The foundation according to this invention comprises hole means defininga shaft in the earth, said shaft hav ing a peripheral sidewall; amonolithic annulus of concrete cast in place in the shaft, having alongitudinal central bore, and having the external peripheral surfacethereof in engagement with said shaft peripheral sidewall, said bore-being large relative to the thickness of said annulus of concrete, theupper end of said annulus of concrete being located to receive andsupport a structure.

These and other aspects of the present invention will become moreclearly apparent, as will the principles and scope of applicability ofthe invention, during the course of the following detailed discussionwhich is keyed from time to time to the preferred embodiments of theinvention that are shown in the attached drawing.

In the drawing:

FIGURE 1 is a vertical sectional view of part of the earth near thesurface showing in longitudinal section a shaft in the earth, a tubularcasing in the shaft and concrete being poured about the shaft/casingannulus;

FIGURE 2 is a sectional view similar to FIGURE 1 showing a succeedingstage wherein a plug of concrete has been poured in the casing and acore of dirt has been used to fill the casing, above the plug;

FIGURE 3 is a sectional view showing a further stage wherein the casinghas been longitudinally upwardly withdrawn from the shaft;

FIGURE 4 is a sectional view which shows a completed foundationaccording to the present invention, wherein the dirt core has beenremoved subsequent to hardening of the concrete and a structure issupported upon the foundation; and

FIGURE 5 is a sectional view similar to FIGURE 1 of an early stage inthe formation of La foundation according to a second embodiment of theinvention wherein the subterranean formation is unstable.

When soil conditions are such that a shaft can be made in the earthwithout substantial seepage into, caving-in or leakage from it, thesteps now to be discussed in regard to FIGURES 1-4 are advantageouslyuseful. Referring to FIGURE 1, as a first step, a hole or shaft 10 issunk, drilled, dug or otherwise formed in the earth typically beingabout forty feet deep and of about five feet in diameter. Next a tubularcasing 12, typically of steel, having an O.D. of less than the diameterof the shaft, typically of about four feet O.D., is lowered into theshaft so as to bottom longitudinally centrally therein and extend to themouth 14 of the shaft 10.

Then plastic, unhardened concrete 15 is pumped into the annulus 16between the casing exterior 18 and the shaft peripheral sidewall 20 tofill the annulus. If desired, an intermediate tubular Ibody ofreinforcing wires can be disposed in the annulus 16 prior to pouring ofthe concrete 15. An axially short plug or point 22 of plastic,unhardened concrete (FIGURE 2) is preferably pumped at about this sametime into the bore 24 of the casing 12, landing at the bottom thereof.The concrete 1S, 22 is advantageously ready-mixed and poured directlyfrom a conventional mixer-transporter truck T from adjacent the shaftmouth 14. In this example, the plug 22 is typically about 3 4 feetthick. The remainder of the casing bore 24 is filled with sand, loam,clay, dirt or similarly non-cohesive granular material 26.

Preferably, before the concrete 15, 22 has hardened, the casing 12 islongitudinally withdrawn (FIGURE 3) from the shaft 10, whereupon thebodies of plastic concrete 15 and 22 merge into one monolithic body. Thesand or similar material 26 prevents implosion of the plastic concreteas the casing 12 is withdrawn and thereafter prevents inward collapse ofthe plastic concrete, giving the latter opportunity to harden.

For certain applications, the sand or similar material 26 can be left inplace after the concrete 15, 22 has hardened and a structure such as ahouse, bridge abutment, bridge, pier, office, apartment or factorybuilding slab supported thereon. Of course in most of the instances justmentioned several foundation elements laterally spaced from one anotherwould need be employed to support one structure. In most instances, thesand or similar material 26 can be removed from interiorly of the cementannulus, once the cement has hardened (FIGURE 4).

This aspect of the invention may be more readily cornprehended uponreference to the following example.

Example I Three approximately forty foot deep, five foot wide shaftswere sunk in the earth near Lake Charles, Louisiana. Concrete of thefollowing composition was prepared:

The first shaft was peripherally cased and filled with the concretewhich was allowed to harden. The second and third foundations werecompleted according to the invention as just described above, thedifference between them being that sand 26 was left in the secondfoundation and removed from the third subsequent to the hardening of theconcrete thereof. The concrete weighed about 140 pounds per cubic footand the sand weighed about 100 pounds per cubic foot, so the second andthird foundations weighed substantially less than the first.

It was found that a safe design load on the shafts is SOO-750 pounds persquare foot of contact surface about the circumference of the respectiveshaft. With the foundations of the invention, the difference of theweight of the concrete put into the shaft and the soil taken out wascomputed and this extra weight added to the column load. Thus the sandfilled core was found to be able to carry more column load than thesolid concrete shaft and the hollow core shaft was found to 4be able tocarry even more column load.

Referring now to FIGURE 5, in instances where leakage of water into theshaft 10, evident looseness of the soil peripherally of the shaft 10 orporosity of the shaft sidewall make the soil about the shaft peripheryunstable, the shaft sidewall can advantageously be treated by owingwater, or bentonite mud, lime, hydraulic cement or other stabilizingslurries thereagainst and allowing the excess to drain to the bottom ofthe shaft. A tubular casing 28 having an O.D. only slightly less thanthe diameter of the shaft 10 is lowered into the shaft 10.

A casing 12 is then emplaced as described with respect to FIGURES l-4and the foundation of FIGURE 5 completed as described with respect toFIGURES l-4, the concrete 15 filling the annulus between the casings 12and 28. The incoming concrete displaces the excess treating fluid up andout of the shaft. Preferably the casing 28 is withdrawn at about thesame time the casing 12 is withdrawn. As shown in FIGURE 5, either orboth the exterior of the casing 12 or interior of the casing 28 isprovided with at least one nearly coextensive longitudinally extendingpipe 30. In emplacing the concrete 15, the plastic, unhardened concreteis pumped from the surface down the pipe or pipes 30 and out the outlet32 thereof near the bottom 34 of the shaft 10.

It should now be apparent that the invention described herein fulfillsall of the objects set forth at the beginning of this specification andthat the description herein clearly relates the principles of theinvention. Because the ernbodiments shown and described can beconsiderably modified without departing from these principles, thepresent invention should be understood as encompassing all suchmodifications as are within the spirit and scope of the followingclaims.

What is claimed is:

1. A method for constructing a foundation comprising:

(a) making a shaft in the earth;

(b) inserting a tubular casing in the shaft, so as to extend throughoutsusbtantially the full depth of the shaft, said casing having anexternal diameter that is smaller than the diameter of said shaft,thereby defining a shaft/ casing annulus exteriorly of the casing;

(c) filling plastic,

annulus;

(d) depositing an axially short plug or plastic unhardened concrete inthe casing interiorly thereof at the lower end thereof;

(e) filling the casing interiorly thereof above said plug with asubstantially non-cohesive, granular material substantially to theheight of concrete in said annulus.

2. The method of claim 1 comprising as further steps:

(f) longitudinally withdrawing the casing from the shaft before theconcrete has hardened;

(g) allowing the concrete to harden.

3. The method of claim 2 comprising as a further step:

(h) removing the substantially non-cohesive, granular material fromwithin the annulus of concrete.

4. The method of claim 3 comprising as a further step disposing andsupporting a structure on the upper end of said annulus of concrete.

5. The method of claim 2 further comprising, prior to step (c):inserting a second tubular casing in the shaft, coaxially with thefirst-mentioned tubular casing, said second tubular casing having anexternal diameter that is only slightly smaller than the diameter ofsaid shaft, thereby defining the radially outer extent of said shaftcasing annulus.

6. The method of claim 5 further comprising, approximately concurrentlywith step (f): longitudinally withdrawing the second tubular casing fromthe shaft before the concrete has hardened.

7. The method of claim 6 further comprising: prior to step (b) directinga flow of lighter-than-unhardenedconcrete soil stabilizing fluid againstthe peripheral sidewalls of said shaft and approximately concurrentlywith step (c) displacing excess of said uid from said shaft/ unhardenedconcrete into the casing annulus with the concrete lled into said shaft/casing annulus.

8. The method of claim 7 wherein the soil stabilizing fluid is onechosen from the group consisting of water, bentonite mud slurry, limeslurry and hydraulic cement slurry.

9. The method of claim 5 further comprising: fastening a generallylongitudinally extending pipe on at least one of the exterior of saidrst-mentioned tubular casing and the interior of the second tubularcasing oriented so that when said casings are bottomed in said shaft,said pipe has an outlet to said shaft/casing annulus near the bottom ofsaid shaft/casing annulus and an inlet near the upper end of saidshaft/casing annulus; and wherein 6 References Cited UNITED STATESPATENTS S/1901 Mouche] 61-56 1/1930 Newton 61-53.66 3/1930 Smith61-53.64 5/1933 Newman 61-53.64 4/ 1936 Christie 61-56 FOREIGN PATENTS2/ 1908 Germany.

JACOB SHAPIRO, Primary Examiner.

U.S. Cl. X.R.

step (c) comprises pumping concrete down said pipe and 15 61-50; 264-31out the outlet thereof.

